DE2048204A1 - Method for producing a master print image by xerography - Google Patents

Description

PATCNTAIJWXLTC

DR. E. WIEGAND D « ⁿ L.-ING. W. NIEMANN

DR. M. KÖHLER DIPL-ING. C GERNHARDT 204 8 204

MÖNCHEN HAMBURG TELEPHONE = 5SS4 7i 8000 MÖNCHEN 15, TELEGRAMS: KARPATENT NUSSBAUMSTRASSE 10

September 30, 1970 Wa 40 101/70 - Ko / B ■ - '-

Fuji Photo Film Co, Ltd., Ashigara-Kamigun, Kanagawa / Japan

Method for producing a master print image by xerography

The invention relates to a new method of xerography, in particular a method of production of a master print image (printing master) by xerography «,. '-

Xerography consists in its general execution form in that a uniform charge is deposited on a photoconductive substrate on an electrically conductive substrate insulating layer is applied under light shading by means of a corona charge, this layer is exposed to the light image to be reproduced to form an electrostatic latent image, and You also use a toner material on the latent image an electrostatic charge of the desired polarity f

is applied to make the image visible. The resulting toner image can be permanently fixed directly to the photoconductive layer or can be transferred to a suitable transfer member. A new application has been developed by using a toner chemically active material which may react with those contained in the photoconductive layer constituents _e A typical example of this application 13 470 / ^f in Japanese Patent Publication 63 or in the

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U.S. Patent 3,226,227 which teaches Toning image, which is an ingredient that promotes hardening of the resinous material in the photoconductive layer or which can combine with an ingredient in the coating, on the photoconductive coating by xerography is formed. The developed recording material is then heated so that it cures imagewise • the coating is effected, resulting in an etch-resistant pattern.

fe Usually the typical combinations exist

of the materials of a polysiloxane resin binder in the photoconductive coating and aluminum oxide or aluminum salts of organic acids as toner, however, in In this case, the silicone resin is not just an inadequate Shows adhesion to a wide variety of metal substrates, but is also difficult to form a photoconductive coating of high photosensitivity to be molded. In addition, the cured coating shows poor durability to chemical agents such as those used as caustic agents. Because of these disadvantages, the Do not carry out the procedure in practice.

A main object of the invention is one

P new combination of resinous binder and toner material, the disadvantages listed above being overcome or can be improved and this results in a new method for producing a master print image by xerography. ■.

The object is achieved by applying a photoconductive insulating coating to a metal base which is an intimate mixture of a photoconductive powder and an electrically insulating resin binder which has chemically active functional groups, which

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can react with isocyanate groups, an electrostatic latent image is formed, this • picture with a, a masked polyisocyanate compound, hereinafter referred to as isocyanate generator, is developed containing toner that developed Plate is heated to a temperature sufficient to form the isocyanate, so that the reaction between the resin binder and the toner material takes place, whereby the resin binder is completely hardened and in organic Becomes insoluble in solvents and finally | only the photoconductive coating removed from the surfaces where no toner deposition has occurred, exposing the metal substrate.

The method outlined above has numerous Advantages, including a strong affinity of the photoconductive coating for a variety of metal substrates, a high resistance of the cured coating to chemical agents and the application of electrophotographic coatings having superior electrophotographic properties. The procedure will further explained below with reference to the drawings.

In Fig. 1 is a cross section of an electrophotographic Material shown, which carries a toner image on the photoconductive "coating. The recording material 1 consists of a conductive base 11 and a photoconductive insulating coating layer 12 which is applied to 11 is present. According to the invention, the base 11 consists of metals, for example zinc, magnesium, aluminum, Copper and the like .. The photoconductive coating 12 consists of an intimate mixture of a finely divided photoconductor, such as zinc oxide, cadmium sulfide, titanium dioxide, lead oxide, or other chalcogenous compounds of zinc,

ORIGINAL

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Cadmium and lead, and a resinous binder. The coating can contain spectral sensitizers as a minor component for the photoconductor or chemical sensitizers included. The resinous binder used must be functional Contain groups that are capable of reacting with isocyanate groups. Such groups are primary -e and secondary hydroxyl and amino groups. Suitable resinous materials include the various types of alkyd resins (drying and non-drying, oil-modified, phenol / formaldehyde resin ^ modified, styrene or acrylic ester modified, Rosin or natural resin modified and the like.) ,. Epoxy esters, for example epoxy esters of dehydrating castor fatty acids, epoxies, vinyl polymers, such as monomers with hydroxyl groups, for example polyvinyl butyral, copolymers or terpolymers from a monomer made from styrene, alkyl acrylates, alkyl methacrylates, vinyl chloride, vinyl acetate, or ethylene and comonomers from the group of hydroxyalkyl acrylates, Hydroxyalkyl methacrylates and allyl alcohol, the polymers also including acidic monomers such as acrylic acid, methacrylic acid, Itaconic acid, crotonic acid, or maleic anhydride may contain. Mutually compatible combinations of these resins can also be used or in some cases, resinous materials used in the process of dissolving the photoconductive layer after Development to the solvent used are insoluble, can be incorporated in a smaller amount.

These resinous materials contain in their molecular structure a primary or secondary hydroxyl groups that can enter into condensation reactions with the isocyanate groups, which are formed from the toner materials at temperatures ranging from 20 to 150 ⁰ C.

INSPECTED

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^"5 V 2046,204

It should be noted that these resins are excellent binder materials for electrophotographic coatings serve and produce coatings at a faster photographic speed than polysiloxane resins. Furthermore, they are the polysiloxanes with regard to the adhesion to metal substrates and the formation of coatings superior, in which the electrostatic charge is rather slow in numerous insulating organic liquids that are used as the carrier liquid for the liquid developer | can. The photoconductive coating 12 typically contains 40 to 80 percent by volume of the photoconductive powder its total volume and the coating thickness is between a few microns and a few tens of microns.

The electrophotographic coating becomes uniform charged in a switched-off light, then exposed to an image made up of light and shadow to be reproduced, whereby the surfaces hit by light lose the surface charge, and thereby an electrostatic one latent image is obtained.

Then the exposed coating is subjected to development treatment using a polyisocyanate, toner containing formers for transferring the latent Image into an actual image. All known development methods can be used of which the liquid development or the electrophoretic ^ development give a developed picture of of the highest quality. The developed image is indicated at 21 in FIG.

The isocyanate former, which is an essential material according to the invention consists of a compound in which the isocyanate group temporarily blocks or

OFHGINALtNSPECTED

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204820A

masked by a suitable component attached to the Isocyanate is bound, below a certain temperature is, above which the added constituent dissociates and regenerates the active isocyanate or educates. Typical isocyanate formers include polyisocyanates made with the following ingredients masked are: phenol, diethyl malonate, alkyl acetoacetate, acetylacetone, secondary aromatic amines, tertiary alcohols, amides, lactams and the like *. Of these, the phenol-masked polyisocyanates are best known, one of which from Bayer A »G, (West Germany) is commercially available under the name "Desmodur AP Stabil"

Aromatic isocyanates are used as isocyanate compounds preferred due to their higher responsiveness. The isocyanate former is conveniently pulverized, a toner for dry development operations such as magnetic brush, cascade or powder cloud development or it can be dissolved in a suitable organic solvent, followed by the solution obtained is dispersed in an electrically insulating non-polar liquid containing the isoyanate can not solve; the resulting dispersion can then be used in liquid development. In the case of Desmodur AP Stabil, ethylacetai; or Methyl ethyl ketone is suitable as a solvent and the carrier liquid for the dispersion can consist of isoparaffinic, normal paraffin! see or cycloaliphatic see Hydrocarbons, halogenate hydrocarbons and the like. exist. The dispersion obtained shows stable electrophoretic properties for a long time Periods. Colorants or other charge control

ORIGINAL INSPECTED

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"■■■■" ■ "'ν ■''"T-'ffl · 3! » '! I !! F' ■ - S m * ">""·'■''■ ■■■■■■ ■■■■ · · ··''■■ ■ :: ■■ ■■■■■ ■■■ ■■■■■■ ... ,,..., J ,,:.:.> Is, |;: ,,, j;

20A620A

Agents can also be added to the masked isocyanate. Colored toners make it easier to do that To assess the quality of the developed image with the naked eye,

In Fig. 2, there is shown a cross section of the electrophotographic material in a state after the developed toner image 21 is impregnated into the photoconductive coating 12 and then the polyisocyanate is formed by heating, whereby the resinous binder in Fig. 12 is entirely in the areas with toner deposition is hardened. Numbers 13 and 14 denote the hardened and unhardened areas of the Coating.

If the impregnation of the toner in the coating is not complete, hardening will only start the surface of the coating, causing unfavorable results.

The impregnation of the toner former 12 can either by heating the materials to a temperature above the melting point but below the DiSBO ziation point a of the isocyanate former, or by exposing the material to the vapor of a solvent for the isocyanate generator.

In the case of the above-discussed with phenols masked products is the appropriate range of the temperature for impregnation toner 140 to 170 ⁰ C.

The curing reaction is carried out at 170 to 1BO ¹ C with the same product and at these elevated temperatures Bogar reactants with low reactivity, such as secondary hydroxyl groups, can enter into a condensation reaction with the isocyanate formed rather quickly.

ORIGINAL INSPECTED

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Like from Pig. 3, the unhardened area is visible by a suitable solvent, including Esters, ketones, aromatic hydrocarbons and the like. Removed. To prevent the danger the burning of the treatment solvent can be chlorinated hydrocarbons or chlorofluorinated hydrocarbons Incorporate or use hydrocarbons. In Pig, 3, 15 denotes the underlying metal released.

Like from Pig. 4, the uncovered base was made by a suitable Xtz solution, for example an aqueous ferric chloride solution, or another acidic solution Etched baths.

Additional operations can also be carried out to improve the image quality of the developed image will. Illustrative examples of such additional Operations is a pre-bath for the material bearing the latent image and the rinsing of the developed one Material prior to the uncured coating removal operation. The former treatment serves

- ■ ■■■ '. ·

to lower the background, while the latter treatment besides lowering the background,, to a The purpose of this is to improve the uniformity of the developed image.

example 1

Manufacture of an electrophotographic recording material

A mixture was sprayed onto a zinc plate from 100 parts by weight of photoconductive zinc oxide, 50 parts of an alkyd resin varnish modified with styrene

ORIGINAL INSPECTED

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" ⁹ " 2043204

(Content of non-volatile $ 50) and 40 parts of toluene absorbed and a dry strength of about 5 Ά obtained (coating weight on dry basis 18 g / m).

Manufacture of the toner (developer)

10 parts by weight Desmodur AP Stabil (Bayer A.G., West Germany; the material consists of a phenol-masked condensate of 3 moles of tolylene diisocyanate and 1 mole of trimethylolpropane) were in 1000 l

Parts of butyl acetate dissolved. 30 parts of the solution were ultrasonic waves in 100 parts of a carrier liquid from 980 parts of kerosene and 20 parts of cottonseed oil. dispersed "

Production of the master print image by electrophotography

The photoconductive coating prepared in the above manner is easily dissolved in toluene. The recording material adapted in the dark was exposed to a negative corona discharge and assumed a uniform electrostatic charge. The assumed λ potential immediately after the end of the corona discharge was about 200 volts. The coating was contact exposed to incident light with a positive slide. After the slide was taken off, the coating was soaked with the isoparaffin solvent Isopar H (product of Esso Standard Oil Co.) and then developed with the developer prepared as above. Since the Desmodur AP Stabil particles take on a positive electrostatic charge in the dispersion, they separate on the surface that holds the charge.

ORlGINAL INSPECTED

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had to hold off and the result was a positive rendition.

The plate still held a thin film of the developer, which was rinsed with the isoparaffin solvent Isopar E (product of Esso Standard Oil Co.). Then the plate was dried by using warm air at about 40 ^{° C.} The plate was then kept in an ^{oven kept at 140 °} C. for 10 minutes, after which the temperature was then increased to 180 ^° C. The plate was held under these conditions for 10 minutes. After that, the curing reaction was over. The plate was immersed in toluene with gentle stirring, the area with toner deposition remaining unchanged, while the entire background area of the photoconductive coating slowly dissolved. The permanent pattern obtained withstood various acidic baths including aqueous ferric chloride.

Example 2

An electrophotographic material was made similar Prepared as in Example 1, but with an epoxy meter of dehydrated castor oil fatty acids an oil length of $ 40 instead of the styrene treated one Alkyd resin used.

A cascade development material was produced by mixing nitrocellulose-coated silica granules and finely divided Desmodur AP Stabil with an average diameter of 20 η . Similarly, using this material, satisfactory results have been obtained.

ORIGINAL INSPECTED

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Example 3

A zinc plate, a layer of 100 parts by weight of photoconductive zinc oxide, 20 parts by weight was a copolymer of butyl methacrylate 6OjS, 25 $> styrene, hydroxyethyl acrylate and 13 $ 2 $ acrylic acid and from 5 wt, parts by a modified alkyd resin with Acrylester (Hydroxyl number 30) applied. The

eflektrophotographische material was in the same manner as in Example 1, treated, however, a mixture of 50 hone toluene and 50 parts of ethyl acetate instead of the used toluenes · Ee were equally good results as obtained in Example 1 ·

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Claims (5)

" ¹² " 2 O 4 ö 2 OA Claims Method for producing an etch-resistant pattern by xerography, characterized in that that on a metal base a photoconductive insulating coating, which consists of an intimate Gemiscli one photoconductive powder and an electrically insulating resin binder containing chemically active functional groups which can react with isocyanate groups, ^ consists, is formed, an electrostatic latent * image is formed on the coating, this latent image with a toner containing a masked polyisocyanate compound, the developed plate is developed is heated to a sufficient elevated temperature to regenerate the isocyanate and the reaction between the resin binder in the photoconductive coating and the polyisocyanate is achieved so that the resin binder fully cured and in organic solvents becomes insoluble, and finally the photoconductive coating on the areas where no toner deposition took place, removed and thereby the metal base is exposed. ) | 2. The method according to claim 1, characterized in that that before the regeneration of the masked isocyanate with the developed toner material a sufficient one Impregnation into the inner part of the photoconductive coating by heating above the melting point, However, below the regeneration temperature of the masked isocyanate, is carried out. 5. The method according to claim 1 or 2, characterized in that a masked polyisocyanate with a phenol masked polyisocyanate is used. ORIGINAL INSPECTED 109816/1890 4. The method according to claim 1 to 3, characterized in that the resin binder is an alkyd resin, an epoxy ester of dehydrating castor oil fatty acids, Vinyl copolymers, the hydroxyalkyl acrylate, hydroxyalkyl methacrylate or allyl alcohol, or compatible combinations thereof can be used. 109816/1890 Empty hurry